Industrial robot

ABSTRACT

There is provided an industrial robot having no interference of a cable for an end effector or the like with a peripheral apparatus. 
     An end effector  5  is fixed to a wrist flange  4  through an intermediate member  6 . The intermediate member  6  takes the shape of a crankshaft in which a first flange  6   a  attached directly to the wrist flange  4 , a second flange  6   b  provided at a predetermined interval in parallel with the first flange  6   a  and attached directly to the end effector  5 , and two members  6   c  and  6   d  for coupling the first and second flanges  6   a  and  6   b  are arranged symmetrically.

TECHNICAL FIELD

The present invention relates to an industrial robot and moreparticularly to a vertical articulated robot for spot welding.

BACKGROUND ART

FIG. 4 is a side view showing a conventional spot welding robot. In FIG.4, 51 denotes a 6-axis vertical articulated robot, 52 denotes a spotwelding gun attached to the tip of the vertical articulated robot 51,and 53 denotes a cable for supplying a welding current to the spotwelding gun.

The vertical articulated robot 51 includes a fixing portion 54, aturning portion 55 supported pivotally on the fixing portion 54 andturned around a vertical axis, a lower arm 56 supported pivotally on theturning portion 55 and rocked in a longitudinal direction, an upper arm57 supported pivotally on the lower arm 56 and rocked in a verticaldirection, and a wrist portion 58 attached to the tip of the upper arm57. The wrist portion 58 has the degree of freedom of a rotation aroundthree axes which are orthogonal to each other and has the spot weldinggun 52 fixed to a tip thereof.

The cable 53 is wired from a welding timer, which is not shown, to thefixing portion 54 and is clamped onto the fixing portion 54 where saidcable is wound around the vertical axis (in a counterclockwise directionseen from above) at the level of the fixing portion 54 and rises up tothe level of the turning portion 55. Furthermore, the cable 53 is woundaround the vertical axis (in a clockwise direction seen from above) atthe level of the turning portion 55 and is clamped onto the turningportion 55. Furthermore, the cable 53 rises upward along the lower arm56, and is hung on a cable stand 59 fixed onto the upper arm 57 and isextended to the spot welding gun 52.

In the conventional spot welding robot, however, the cable 53 is lifteddynamically above the upper arm 57 with providing certain looseness.Therefore, there is a problem in that the cable 53 interferes with aperipheral apparatus or the like. Moreover, there is a problem in thatthe cable 53 is rubbed with the peripheral apparatus or the like and isthus worn out. Furthermore, there is also a problem in that theoperation of the wrist portion 58 is limited if the looseness of thecable is decreased to avoid the interference with the peripheralapparatus or the like.

Although the cable 53 provided to have the looseness above the upper arm57 is rocked according to the operation of the robot where said rockingmotion is difficult to be predicted with accuracy. Therefore, anotherproblem is that the interference of the cable with the peripheralapparatus cannot be checked in the simulation such as by offlineteaching.

DISCLOSURE OF THE INVENTION

Therefore, it is an object of the invention to provide an industrialrobot having no interference of a cable for an end effector or the likewith a peripheral apparatus.

In order to solve the problems, the invention provides an industrialrobot in which an end effector is attached to a tip of a wrist portionprovided on a tip of an arm, and a cable or the like for supplying apower, a signal or a material to the end effector is provided from thearm to the end effector, wherein the end effector is fixed to the wristportion through an intermediate member, and the intermediate member isformed in a shape of a crankshaft in which a first flange attacheddirectly to the wrist, a second flange provided at a predeterminedinterval in parallel with the first flange and attached directly to theend effector, and two members provided in a position placed apart fromcenters of the first and second flanges and serving to couple the firstand second flanges are arranged symmetrically. Moreover, the wristportion includes a wrist base rotated axially in a longitudinaldirection of the arm and a fixing member attached to the wrist base androtated integrally with the wrist base, clamps the cable or the likeonto the arm and winds the cable or the like upon the arm axially in thelongitudinal direction of the arm, further bends the cable or the liketo be U-shaped and changes a direction thereof, winds the cable or thelike upon the arm in a reverse direction and clamps the cable or thelike onto the fixing member, and further extends the cable or the liketo the end effector. Furthermore, the cable or the like is divided intotwo portions and the two portions are coupled through a connectorattached to the fixing member. In addition, a portion of the cable orthe like which is wound upon the arm is covered with a cylindricalmember.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing the upper arm of an industrial robotaccording to an embodiment of the invention and

FIG. 2 is a plan view.

FIG. 3 is an explanatory view showing an intermediate member seen in anAA′ line of FIG. 1.

FIG. 4 is a side view showing a spot welding robot according to theconventional art.

FIG. 5 shows the cable being made of two portions with a connector.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the invention will be described below with reference tothe drawings. FIG. 1 is a plan view showing the upper arm of anindustrial robot according to the embodiment of the invention and FIG. 2is a side view showing the same, a part of which is shown in a sectionfor convenience of explanation.

In the drawing, 1 denotes the upper arm of a so-called 6-axis verticalarticulated robot. The tip of the upper arm 1 includes a wrist portionhaving a wrist base portion 2 to be rotated around a first wrist axis 21in the longitudinal direction of the upper arm 1, a wrist rocking member3 to be rocked around a second wrist axis 22 which is orthogonal to thefirst wrist axis, and a wrist flange 4 to be rotated around a thirdwrist axis 23 which is orthogonal to the second wrist axis 22.

5 denotes a spot welding gun which is an end effector fixed to the wristflange 4 through an intermediate member 6. The intermediate member 6 isconstituted by a first flange 6 a fixed directly to the wrist flange 4,a second flange 6 b provided at a predetermined interval in parallelwith the first flange 6 a and serving to directly fix the spot weldinggun 5, and connecting members 6 c and 6 d for coupling the first flange6 a to the second flange 6 b. The connecting members 6 c and 6 d areprovided in parallel with each other symmetrically with respect to thethird wrist axis 23 in the side view (FIG. 2), and furthermore, they areoffset to either side with respect to the third wrist axis 23 in theplan view (FIG. 1). Because of such a structure, the intermediate member6 takes the shape of a crank in the plan view (FIG. 1).

7 denotes a welding cable which is a wiring and piping bundle forsupplying a welding current, a power for gun driving, cooling water, anoperation signal or the like to the spot welding gun 5. 8 denotes afirst fixing member fixed to the wrist base 2 and rotated around thefirst wrist axis 21 integrally with the wrist base 2, and 9 denotes asecond fixing member fixed to the wrist rocking member 3.

In the same manner as in the example according to the conventional art,the welding cable 7 is extended to the upper arm 1 from a welding timerwhich is not shown through the fixing portion, the turning portion andthe lower arm of the robot, is fixed onto the upper surface of the upperarm 1 through a clamp 10, is wound clockwise (as seen from the wristside) around the upper arm 2 taking a cylindrical shape and reaches thelower surface of the upper arm 1. The welding cable 7 is bent like a Ushape at the lower surface of the upper arm 1, is then wound in areverse direction, that is, a counterclockwise direction around theupper arm 1, reaches the upper surface of the upper arm 1 again, isfixed to the first fixing member 8 through clamps 11 and 12, passesthrough the side of the wrist rocking member 3 and is fixed to thesecond fixing member 9 through a clamp 13. When taking a posture shownin FIGS. 1 and 2, that is, such a posture that the first wrist axis 21and the third wrist axis 23 are coaxial with each other, the firstfixing member 8 and the second fixing member 9 are attached in such amanner that the clamp 12, the center of the second wrist axis 22 and theclamp 13 are arranged on a straight line. Furthermore, the welding cable7 reaches the spot welding gun 5 through a portion between theconnecting members 6 c and 6 d of the intermediate member 6 and is fixedto the spot welding gun 5 through a clamp 14.

15 denotes a guide member. The guide member 15 is a cylindrical memberin concentric with the upper arm 1 (a section thereof is shown in thedrawing), and serves to cover a portion of the welding cable 7 which iswound upon the upper arm 1 (a portion from the clamp 10 to the clamp11), thereby holding the welding cable 7 in a doughnut-shaped spacebetween the upper arm 1 and the guide member 15.

When the wrist base 2 is rotated around the first wrist axis 21, thewelding cable 7 is guided by the guide member 15 and follows the motionof the wrist base 2 by a moving bend on a circumference around the upperarm 1 (an operation in which one of the portions is wound upon the upperarm 1 so as to be long and the other portion is wound to be short with aU-shaped bent portion set to be a boundary).

When the wrist rocking member 3 is rocked around the second wrist axis22, the welding cable 7 follows the motion of the wrist rocking member 3by a bend between the clamp 12 and the clamp 13. At this time, since thewelding cable 7 is bent in almost the same plane, there is a smalldanger that it might come in contact with a peripheral apparatus or thelike or might be caught thereon.

FIG. 3 is an explanatory view showing the intermediate member 6 seen inan AA′ line of FIG. 1. As shown in FIG. 3, the welding cable 7 fixed tothe wrist rocking member 3 (not shown) through the clamp 13 passesthrough the center of the third wrist axis 23 from below theintermediate member 6, and furthermore, passes through a portion betweenthe connecting members 6 c and 6 d to come upward out of theintermediate member 6 and is fixed to the spot welding gun 5 (not shown)through the clamp 14. Since the welding cable 7 is thus provided, thewelding cable 7 is bent in the intermediate member 6 to follow therotation of the wrist flange 4 around the third wrist axis 23 when thewrist flange 4 is rotated around the third wrist axis 23.

The connecting members 6 c and 6 d are provided with an offset from thethird wrist axis 23 and the intermediate member 6 is caused to take theshape of a crankshaft in order to avoid the interference of theconnecting members 6 c and 6 d with the welding cable 7 and to maintainthe operating range of the wrist flange 4 around the third wrist axis23.

Moreover, the second fixing member 9 does not need to be provided. Insome cases in which the welding cable 7 is not fixed to the wristrocking member 3 depending on the axial structure of the wrist portion(for example, a center distance) or the rigidity of the welding cable 7,the followability of the welding cable for the operation of the wristportion can be more excellent.

In place of the clamp 14, moreover, the welding cable 7 may be fixed atthe upper portion of the intermediate member 6 (which is indicated asthe designation F in FIG. 3).

If the welding cable 7 is cut between the clamp 11 and the clamp 12 andis thus divided into two portions 7 a and 7 b to be connected through aconnector 70, and the connector is fixed to the first fixing member 8,furthermore, the spot welding gun 5 can be repaired and exchangedconveniently.

While the spot welding robot has been taken in the description of theembodiment, the invention is not restricted to the spot welding robotbut can be applied to many uses such as painting, sealing, abrasion andhandling. In other words, the end effector may be a spray gun forpainting, a nozzle for sealing, an abrading tool, a mechanical hand orthe like, and a cable or the like may be a hose for painting, a sealantsupply hose, an air hose for driving a pneumatic tool, a power line fordriving a power tool or the like.

As described above, according to the invention, the cable for the endeffector or the like is provided along the upper arm and the wrist.Therefore, it is possible to prevent the interference of the cable orthe like with the peripheral apparatus or the like, and furthermore, itis possible to obtain such an advantage as to prevent the damage of thecable or the like from being caused by the interference.

Moreover, the motion of the cable or the like with respect to the upperarm is restricted to a constant space. In a simulation such as offlineteaching, therefore, it is also possible to obtain such an advantagethat the interference of the cable or the like with the peripheralapparatus or the like can easily be checked.

INDUSTRIAL APPLICABILITY

The invention is useful as an industrial robot and more particularly asa vertical articulated robot for spot welding.

1. An industrial robot comprising: an arm; a wrist portion provided on atip of the arm; an intermediate member; an end effector attached to atip of the wrist portion through the intermediate member; and a cableprovided from the arm to the end effector for supplying a power, asignal or a material to the end effector, wherein the intermediatemember comprises: a first flange attached directly to the wrist portion;a second flange provided at a spaced interval in parallel with the firstflange and attached directly to the end effector; and a connectingmember provided in a position placed apart from centers of the firstflange and the second flange, wherein the connecting member couples thefirst flange and the second flange, and provides a space between thefirst flange and the second flange, and the cable passes through thespace.
 2. The industrial robot according to claim 1, wherein the cablepasses through the space such that the cable intersects with a rotatingaxis of the tip of the wrist portion.
 3. The industrial robot accordingto claim 2, wherein the connecting member is arranged with an offsetfrom the rotating axis of the tip of the wrist portion so as to avoidinterference between the connecting member and the cable.
 4. Theindustrial robot according to claim 3, wherein the connecting memberincludes a first connecting member and a second connecting member thatare arranged symmetrically with respect to the rotating axis of the tipof the wrist portion.
 5. The Industrial robot according to claim 1,wherein • the cable is fixed at a tip portion of the arm.
 6. Theindustrial robot according to claim 5, wherein the cable is fixed at thewrist portion.